Methods to increase structural performance, strength and durability of fabric-reinforced composite materials by pre-stressing

Abstract

Methods to increase structural performance, strength, and durability of textile-reinforced composite materials are provided. The textile reinforcement may be knitted, for example, in a flat bed weft knitting machine. The method may include pre-stressing a textile reinforcement preform by applying tension. A polymeric precursor may be introduced to the pre-stressed textile reinforcement preform. The polymeric precursor may then be cured or consolidated, followed by releasing of the applied tension to form the composite article comprising polymer and the pre-stressed textile reinforcement. In other aspects, a composite article is provided that has a pre-stressed textile reinforcement structure and a cured polymer. The textile reinforcement may be a knitted, lightweight, seamless, unitary structure. The knitted reinforcement structure may have distinct first and second knitted regions with different levels of pre-stress, thus providing enhanced control over strength, rigidity, and flexibility of the composite article.

What is claimed is: 
     
       1. A method of making a load bearing composite article comprising:
 placing a textile reinforcement preform into a three-dimensional formwork, wherein the composite article has a shape defined by the three-dimensional formwork; 
 pre-stressing the textile reinforcement preform by applying uniaxial tension thereto; 
 introducing a liquid polymeric precursor into the pre-stressed textile reinforcement preform to partially or fully fill openings in the textile reinforcement preform after the textile reinforcement preform is placed into the three-dimensional formwork; 
 curing the polymeric precursor; and 
 releasing the applied tension to form the load bearing composite article comprising a cured polymer embedding the pre-stressed textile reinforcement. 
 
     
     
       2. The method of  claim 1 , further comprising forming the textile reinforcement preform prior to the pre-stressing. 
     
     
       3. The method of  claim 2 , wherein the forming comprises knitting the textile reinforcement preform into a unitary seamless structure. 
     
     
       4. The method of  claim 3 , wherein the knitting is conducted on a computer numerical control (CNC) flat bed weft knitting machine. 
     
     
       5. The method of  claim 3 , wherein the knitting forms a first knitted region and a distinct second knitted region in the textile reinforcement preform, wherein the first knitted region and the second knitted region vary from one another by at least one property selected from the group consisting of: stitch pattern, stitch density, stitch length, stitch spacing, yarn composition, yarn thickness, yarn denier, yarn weight, yarn ply, yarn degree of twist, rigidity, flexibility, and combinations thereof. 
     
     
       6. The method of  claim 1 , wherein the introducing of the polymeric precursor is only to select regions of the pre-stressed textile reinforcement preform. 
     
     
       7. The method of  claim 1 , wherein the introducing of the polymeric precursor is to the entire pre-stressed textile reinforcement preform. 
     
     
       8. The method of  claim 1 , wherein the knitted reinforcement structure comprises a first knitted region and a distinct second knitted region, and the pre-stressing creates a first pre-stress level in the first knitted region and a second pre-stress level in the distinct second knitted region that is greater than the first pre-stress level. 
     
     
       9. The method of  claim 8 , wherein the first knitted region has a first rigidity level and the second knitted region has a second rigidity level, wherein the first rigidity level is at least 25% greater than the second rigidity level. 
     
     
       10. The method of  claim 1 , wherein the liquid polymeric precursor forms a cured thermoset polymer selected from the group consisting of: epoxies, polyesters, polyimides, phenols, bismaleimides, polyurethanes, derivatives, copolymers, and combinations thereof. 
     
     
       11. The method of  claim 1 , wherein the pre-stressed seamless knitted reinforcement structure comprises a yarn selected from the group consisting of: carbon fiber, glass fiber, polymeric fibers, metal fibers, and combinations thereof. 
     
     
       12. The method of  claim 1 , wherein the pre-stressed seamless knitted reinforcement structure comprises a yarn selected from the group consisting of: carbon fiber, glass fiber, aramid fibers, polyelastane fibers, polyolefin fibers, thermoplastic monofilaments, and combinations thereof. 
     
     
       13. A method of making a load bearing composite article comprising:
 placing a textile reinforcement preform into a three-dimensional formwork, wherein the composite article has a shape defined by the three-dimensional formwork; 
 pre-stressing the textile reinforcement preform by applying uniaxial tension thereto; 
 introducing a liquid polymeric precursor into the pre-stressed textile reinforcement preform to partially or fully fill openings in the textile reinforcement preform after the textile reinforcement preform is placed into the three-dimensional formwork; 
 curing the polymeric precursor; and 
 releasing the applied tension to form the load bearing composite article comprising a cured polymer embedding the pre-stressed textile reinforcement, wherein the load bearing composite article is a structural component for at least one of an automotive structure, an aerospace structure, a rail structure, a ship structure, a transportation structure, an infrastructure structure, or an architectural structure. 
 
     
     
       14. The method of  claim 13 , wherein the forming comprises knitting the textile reinforcement preform into a unitary seamless structure. 
     
     
       15. The method of  claim 14 , wherein the knitting is conducted on a computer numerical control (CNC) flat bed weft knitting machine. 
     
     
       16. The method of  claim 14 , wherein the knitting forms a first knitted region and a distinct second knitted region in the textile reinforcement preform, wherein the first knitted region and the second knitted region vary from one another by at least one property selected from the group consisting of: stitch pattern, stitch density, stitch length, stitch spacing, yarn composition, yarn thickness, yarn denier, yarn weight, yarn ply, yarn degree of twist, rigidity, flexibility, and combinations thereof. 
     
     
       17. The method of  claim 13 , wherein the introducing of the polymeric precursor is only to select regions of the pre-stressed textile reinforcement preform. 
     
     
       18. The method of  claim 13 , wherein the introducing of the polymeric precursor is to the entire pre-stressed textile reinforcement preform.